The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 29, 1992
Filed:
Mar. 28, 1990
Yasuo Ito, Inagi, JP;
Hiroshi Kyogoku, Nishimine, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
Image reading apparatus having a D/A converter with a controllable output includes a light source for illuminating an original image. A reading device is provided for photoelectrically reading the original image illuminated by the light source and generating an analog image signal. A D/A converter is provided having a digital input terminal, an analog output terminal, and a reference terminal. The analog image signal generated from the reading device is applied to the reference terminal. The D/A converter attenuates the level of the analog image signal applied to the reference terminal based on a damping factor corresponding to the digital data applied to the digital input terminal. The thus-attenuated analog image signal is then output to the analog output terminal. An amplifier is provided for amplifying the attenuated analog image signal output from the analog output terminal of the D/A converter. An A/D converter is provided for converting the amplified analog image signal output from the amplifier into a digital image signal. Control circuitry is provided for controlling the digital data applied to the digital input terminal of the D/A converter to cause the analog image signal supplied to the A/D converter to have a predetermined level. This provides an analog image signal having a constant signal level even when the brightness of the light source, (e.g., a fluorescent lamp) varies widely.